In FY 2019, we continued our efforts to understand the impact that phenol-soluble modulins have on biofilm development. We have completed our set of isogenic deletion mutants in S. epidermidis psm loci to investigate the role all PSMs play in S. epidermidis biofilm development and dissemination from device-related infection in vivo and have analyzed the impact of all PSMs on S. epidermidis biofilm formation. Furthermore, we have started a more encompassing analysis of sepsis caused by coagulase-negative staphylococci, which includes research on S. haemolyoicus and S. aureus in addition to S. epidermidis. This research addresses one of the most frequent and severe complications of biofilm formation on indwelling medical devices by staphylococci. Finally, we completed a project investigating the reasons of advantages quorum-sensing mutants have in S. aureus biofilm infection.